Variable resistance and system controlled thereby



June 4, 1929. JUERS 1,715,761

VARIABLE RESISTANCE AND SYSTEM CONTROLLED THEREBY Filed Jan. 3. 1925 2 Shets-Sheet 1 INVENTOR J. H. JUERS June 4, 1929.

VARIABLE RESISTANCE AND SYSTEM CONTROLLED THEREBY Filed Jan. 3. 1925 2 Sheets-Sheet 2 Fly. 10.

Patented June 4, 1929.

UNITED STATES JOHN HENRY J'UERS, OI NEW YORK, N. Y.

VARIABLE RESISTANCE AND SYSTEM CONTROLLED THEREBY.

Application filed January-3, 1925. Serial No. 335.

The invention relates to resistance devices and systems for controlling electric circuits.

One of the principal objects of the invention is to provide a novel and comparatively simple, though reliable and efficient, means for voltage regulation and for speed regulation for electric motors.

Other objects and advantages will appear as the invention is hereinafter disclosed.

Referring to the drawings which illustrate what I now consider preferred forms of the invention: I

Fig. 1 is an end elevation of an electric dynamo having the variable resistance device applied thereto.

Figs. 2 and 3 are respectively an inverted plan view and a detail side elevation, partly in section, of the apparatus shown in Fig. 1..

Fig. 4 is a wirln diagram.

Fig. 5 is an end e evation of another form of the variable resistance device in combination with a wiring diagram.

Figs. 6, 7 and 8 are side elevations and see tons of details contained inthe device shown 5 in Fig. 5.

Fig. 9 is a diagram illustrating-the distribution of forces and moments in the device shown in Fig. 5. I

Fig. 10 is still another form of variable resistance in combination with a wiring dia gram.

I have discovered that a series of two or more relatively rotatable carbon discs or rollers in contact with each other and all rotating under the influence of contact friction when one member of said series is rotated or driven, will form a resistance device having many desirable characteristics. By vary ing the pressure of contact, as by moving the discs (rollers) relatively towards and away from each other, without, however, com pletely separating the same, the contact resistance of the series may be varied through a comparatively wide range. The discs (rollers) of course, may be of various dimensions in regard to diameter, thickness or length. The shape of the contact surface may also vary so that contact between discs (rollers) may be established either at a single point or at a straight line, the length of which may vary to suit the particular use to-which the resistance device is to be put. The total number of discs (rollers) may be grouped in P various ways so as to givecontact resistance in parallel or in series or in a combination of both. Finally, some or all of these variable factors may be combined and a large variety of variable resistances lVhile the invention may e applied to other systems within the scope of at least some of the appended claims, it-is admirably adapted to be employed in voltage regulating systems for generators as shown diagrammatically in Figs. 4 and 5, or for hand regulated systems for various purposes, one of which is shown in Fig. 10. While the diagrams of Fig. 4 and Fig. 5 illustrate the variable resistance device in connection with circuits of electric generators only, it will be understood by all familiar with the art that said device can also be used in connection with circuits of electric motors for speed regulating purposes and I shall now proceed to fully describe said variable resistance device.

Referring to Fig. 1, a carbon disc 10 is mounted for rotation about its axis but is otherwise fixed. Another carbon disc 11 is mounted for rotation about its axis 12 and for bodily swinging movement toward and away from the first disc 10, this being effected by mounting the shaft or spindle 12 of the disc 11 in one or more lever arms 13, fulcrumed on'a stationary pivot 14. By constructing the element 12, and the shaft of the disc 10 of metal, electric current maybe conveniently conveyed to and from the discs. The 'discs10 and 11 are normally held in contact with each other by means of a tension spring 16 secured at one end to the arm or arms 13 and relatively fixed at its other end. By virtue of this construction the disc 10, when rotated by any suitable means will serve as a driver of the other disc 11, to cause the latter to rotate about its own axis. 'An

electromagnet 17 is adapted to attract the end of the arm or arms 13 opposite the spring 16 and to relieve the contact pressure etween the discs 10, 11, to an extent dependent on the strength of the .current through the coil of. the electromagnet. While the arm or arms 13 may be provided with an armature adapted to cooperate with the electromagnet, I prefer to construct the arm or arms 13 of magnetilzable material such as soft iron orsilicon stee In Fig. 4 the coil of the electromagnet 17 is shown connected across the terminals in a D. C. shunt wound generator which comprises the armature 18 and shunt field winding 19, this generator being, for exam le, one employed for use on an automobile or batina thus be obtained.

. it will be note frame or chassis and d that one terminal of the generator is grounded and the other terminal is connected to one terminal of the storage battery 20 and to one terminal of each of a plurality of electric lamps 21, 22. The other terminals of the battery and lamps are grounded, these-called ground being the connected parts of the automobile. The shunt field winding 19 is serially connected with the discs 11- 10. The

design is such that the system operates sub stantially as follows:

Assuming that the voltage across the terminals of the generator remains constant and at the desired value, the current through the coil of'the magnet 17 remains constant and the contact resistance between the rotating discs 10-11 is constant. If, for any'cause, the terminal E. M. F. of the generator rises (or falls), the following action takes place.

The current through the coil of magnet 17 rises (or falls) the pull of the magnet on the arm or arms 13 increases (or decreases) the contact pressure of the disc 11 on the disc 10 decreases (or increases) the contact resistance between the discs 11-10 increases (or decreases) 5 the shunt field current decreases (or increases) and the E. -M. F. generated by the dynamo decreases (or increases) until it again reaches the desired predetermined value. The terminal voltage of the generator is thus automatically maintained substantially constant at the desired value for charging the battery and lighting the lamps, even though the speed of the generator may vary considerably.

It will be noted that the resistance between the discs 1011 is contact resistance,

it being intended that the discs shall not completely separate. The resistance device 1011 is not a make and break device, so that sparking or arcing is a n'iinimu-m. Moreover, any sparks or arcs between the discs 10 11 due to vibrations, such as the vibration of an automobile, can do no damage since the discs are constantly rotating. In consequence of this rotation individual points of contact of both discs have suflicient time until they meet again, to radiate the heat generated at the moment of contact, into the surrounding medium and thus an excessive or dangerous rise of temperature of the discs will always be avoided. .By adjusting the tension of the spring 16, the voltage at which the system will automatically be maintained, may be selected at will, within practical limits.

In Figs. 1, 2 and 3, I have shown a now prefered form of mechanical construction of the apparatus adapted to be wired and operated as disclosed in connection with Fig. 4;

Referrin to Figs. '1, 2 and 3, it will be noted that t e carbon disc 10 is secured to the shaft 25 of the, generator to rotate therewith.

The frame 26 of the generator comprises an end' plate or hell 27 to which the pivot stud 14 is securely fastened. Two arms, 13, 13, are provided, these arms being secured in spaced apart-relationship by means of a screw or b0lt-28 and spaced sleeve 29 at one end and by means of a screw or bolt 30 and spacing sleeve 31 at the other end. The disc 11 is mounted upon the shaft 12 between the two arms 13, 13, and insulated therefrom by means of suitable insulating bushings and washers as shown .in Fig. 2. It will be noted further that the shaft 12 serves as a binding ost to receive the conductor which conveys current to and from the disc 11. The tension spring 16 is shown to be held at one end in a groove in sleeve 29 and at its other end by a screw 35 which passes through the flange of an angle plate 36 and is provided with a thumb nut 37. The plate 36 is secured to the end plate of the generator.

screw or bolt 41 on the side of the pivot 1 1- remote from the spring 16. Preferably, a stop 50 is provided to limit the swinging movement of the arms 13 so as to prevent complete disengagement of the discs 11 and 10. However, even though the discs 10 and 11 should separate, due to excess vibration or any other cause, the regulating means would still function and arcing between the discs 10 and 11 would cause practically no damage. Another form of the resistance device, adapted to carry comparatively large currents, is illustrated in Fig. 5, where a number of contact-resistance-clements 100, 101, 102 and 103 are held together by means of a tension spring 104. Element 100 is a carbon roller, equipped with a number of smooth ably supported in bearings l08, as shown in' Fig; 6, which is a side elevation of element 100 in assembly. One of the bearings 108 carries a binding post to receive the conductor which conveys current to or away from the carbon roller 100. By means of a suitable member 109 (pulley, gear, sprocket), securely fastened to shaft 106, roller 100 may be rotated, when driven by a motor 110 and will in turn drive elements 101, 102 and 103 (see Fig. 5).

The elements 101, 102 and 103 are made up of carbon discs, one of which is shown in an enlarged section in Fig. 8. Each disc is By virtue of the structure above described,

p 114 of bearings 108 which allow the elements equipped with a bushing 111, made of a suitercised by able self-lubricating, but current-conducting, material, and has a smooth running surface 112. When fully assembled, all running surfaces of the discs are in contact with each other as well as those of element 101 with those of roller 100. All carbon discs are mounted for rotation on stationar shafts in the manner shown in Fig. 7, whic is a side elevation of element 103, full assembled. The shafts of elements 101 and 102 are securel held in suitably constructed insulating ushings 113, supported in extensions to move toward and away from element 100.

The stationary shaft, carrying the discs which make up element 103, is suitably insu-. lated from and supported b arms 115, each of which is pivoted for odily swinging movement toward and away from element 102, in a base 116. This shaft also serves as a binding post to receive the conductor which conveys current to or from the discs of element 103. Crossbars 117, connecting arms 115, are made of magnetiz'able material. One of these crossbars is placed in such a position that the pull of an electromagnet 118 upon said crossbar, will directly oppose the tension of spring 104. The other crossbar issituated at the end of arm 115 remote from the spring in such a manner that the pull exanother electromagnet 119 will sup ort t e tension of spring 104.

T e coil energizing magnet 118 is connected across the terminals of a D. O. shunt wound generator, whose armature 120, and field winding 121, are diagrammatically shown in Fig 5.

he coil energizing magnet 119 is shunted in a well known manner to a resistance in the main line 122 of the generator, so that the current flowing through this coil is always proportional to the line current in 122. The diagram in Fig. 5 also shows the variable resistance connected in series with the field winding 121. The variable resistance depends upon the pressure exercised by element 103 against element 100 through elements 102 and 101..

Fig. 9 shows the diagram of forces and moments governing the value of this pressure. In this diagram S isthe tension of spring 104; T the pull of magnet 118 and U the pull of ma net 119. The resulting pressure P is the force determining the magnitude of the resistance and this pressure is expressed by the equation P= (ST) a/ o-t Ub/o The operation of the variable resistance is as follows: At rest the contact-resistance of is essentially the same as most entirely counteract the tension of s'pr' 104. While this condition revails the seco r id member at the ri ht of t e above equation will be 0- (zero)'; will be g minimum and all conditions.

Having described the function of my variable resistance device as a voltage regulatng means for generators, I do not consider it necessary to describe its function as a speed regulating device for electric motors, since this will readily be understood by all familiar with the art. In Fig. 10 the variable resistance device is shown applied to control the current in, say, an illumination circuit. The device proper the one described before, with the exception that the tension of spring 204 is counteracted by the tension of another spring 205 which may be increased or decreased by means of a screw 206 and handwheel 207, resulting in a decrease or increase of pressure between the carbon discs and a consequent increase or decrease of current in the illumination circuit 208.

In accordance with the provisions of the patent statutes, I have herein described the principle of operation of'm invention, together with the apparatus which I now consider to represent the best embodiments thereof, but I desire to have it understood that the apparatus disclosed is only illustrative and that the invention can be carried out by other means. Also, while it is designed to use the various features and elements in the combinations and relations described,

some of these may be altered and others omitted and some of the features of each modification may be embodied in the others without interfering with the more general results outlined, and the invention extends to such use.

What I claim is 1. A variable resistance device comprising in combination, a pair of rotatable discs one of which is adapted to be frictionally rotated by contact with the other, and means for moving said discs relatively toward and away rom each other to vary the electrical resistance of contact between them.

2. A variable resistance device comprising, in combination, a plurality of relatively rotatable disks,'said disks being contact with each other whereby rotation of one causes rotation of all the disks, means normally maintaining said disks in contact, and

both these causes is an increase means for automatically varying the pressure of contact between said disks to vary the resistance of said device.

3. A variable resistance device compris-.

ing, in combinatiom'a' plurality of contacting rotatable disks, means to cause rotation of said disks whereby the contacting surfaces between adjacent disks are continuously changed, and means for automatically varying the areas of the surfaces of contact existing between adjacent disks by controlling the pressure exerted between the said disks at their contacting surfaces whereby the conducting characteristics of said device is varie i 4. A variable resistance device comprising, in combination, a plurality of rotatable disks, said disks being so arranged as to permit flow of current between any two contactingdisks, means to cause rotation of said disks, and means to increase or decrease the contacting area of two contacting disks durin the relative rotation of said disks.

5. variable resistance device comprismg, in combination, a plurallty of rotatable I disks, means for rotating said disks, means for yieldingly urging said disks toward each other 1n contactin relation, and electrically controlled means for varying the contacting JOHN HENRY JUERS. 

